10 year old girl - sudden potential ASD diagnosis - please anyone similar

Good morning

After a few months of high anxiety with our 10 year old girl - seemingly out of the blue - we have now been told she may have ASD. From nothing to a situation which has spiralled every day to the point that she didn't attend school for the last month, to problems sleeping, major meltdowns (one which ended up in A and E, bad idea on reflection but we were frightened!)...........how has this been masked for so long? We are in a terrible state as a family, walking on eggshells, life being put on hold as our daughter won't do a lot of things, a 7 year old boy who is petrified and despite CAMHS being involved have now been told everything will take months.............